1. Field of the Invention
The present invention relates to a printing paper which is suitable for use in printing apparatus, and more particularly to a printing paper for providing a print having a particular form, in which an image is printed over substantially the whole surface thereof by an image forming apparatus which moves in a reciprocating manner printing paper to form plural images of various colors so as to overlap each other, thereby giving a color image. The present invention also relates to a print forming process and a printing system.
2. Related Background Art
With the increased popularity of apparatus from which image data can be obtained with ease, such as digital video cameras and digital cameras, there is recently an increase in demand for color image printing apparatus which form a color image on printing paper on the basis of the image data obtained. Printing systems of such color image printing apparatus include, for example, a thermal transfer system and the like. Printing using the thermal transfer system is conducted by arranging an ink sheet, on which a thermal sublimation or hot-melt ink has been coated, in close vicinity to printing paper, selectively heating the ink sheet by a thermal head to transfer the sublimated or melted ink to the printing paper, thereby forming an ink image on the printing paper. A thermal transfer printing apparatus, in particularly, a sublimate-type thermal transfer printing apparatus, by which such printing of the thermal transfer system is conducted, may be used as a printing apparatus to conduct printing on printing paper on the basis of image data obtained from a digital camera or the like to provide a high-quality full-color image.
Apparatus for forming a high-quality full-color image other than those described above, for example, Print Club (trade name) by which a photographic image is formed on a small size sticker that can be easily stuck on a purse, pocket notebook or the like, and films equipped with a lens, which is portable to take photographs and the like have been widely used in recent years. Owing to the increased popularity of these apparatus, prints with high-quality full-color images have been utilized in a form that can be stuck on or put into purses or pocket notebooks to be carried around so that one can appreciate them or show or exchange them with others.
Therefore, prints in the form that can be stuck on or put into purses, pocket notebooks or the like to be carried around are required even of prints prepared by means of a digital camera or the like. There is thus a demand for the development of a printing system which can form such a print. More specifically, with the increased popularity of telephone cards, credit cards and the like, purses and pocket notebooks where such cards can be stored with ease have been widely used. Therefore, there is a demand for the development of a printing system which can form a print of the same size as such cards. The specific form of the telephone cards and credit cards in use is a rectangle of 54 mm×85.5 mm as illustrated in FIG. 12, with their four corner edges rounded in the form of an arc and having a curvature radius R of 4 mm. On the other hand, as printing paper which can provide prints that can be stuck on optional articles, there is so-called label type printing paper (label printing paper) of a constitution like a sticker.
To obtain a print in such a form, the printing paper is generally required to be moved in a reciprocating manner in a printing apparatus, such as a thermal transfer providing apparatus, to form plural images of various colors so as to overlap each other, thereby giving a color image. As a result, image cannot be formed on at least a portion of the ends of the printing paper because the printing paper is required to be supported without detaching it upon printing. Therefore, the resulting print contains a blank portion. In other words, since the size of an image which can be formed is limited in the color image printing apparatus, it is impossible to provide a print in which an image has been formed over the whole surface thereof like a silver salt photograph.
In order to solve such a problem, for a process for providing a print in which an image has been formed over substantially the whole surface thereof, it is known to use printing paper provided with an easy-cut structure 32 by which the printing paper can be easily cut, such as perforations formed of an intermittent cut at both sides in a conveying direction of the printing paper so as to cut outside portions 34 off with ease as illustrated in FIG. 13.
FIG. 16 is a typical side view in the case where the printing paper is label printing paper. As illustrated in FIG. 16, the label printing paper comprises an upper image-receiving layer portion 41 which will become a print which can be stuck on an article, and a lower supporting layer portion (separator) 42 which covers an adhesive portion of the image-receiving layer portion 41 before use to protect it. The image-receiving layer portion 41 has a sealing substrate 44 positioned in the center, a receiving layer 43 provided on the upper surface thereof and receiving coloring materials such as inks for forming an image, and an adhesive layer 45 provided on the lower surface of the seal substrate 44 and having tackiness capable of being stuck on an article. The supporting layer portion 42 has a supporting substrate 47 and a releasing layer 46 provided on the upper surface thereof, through which the image-receiving layer portion 41 can be released, without impairing the tackiness of the adhesive layer 45. By using the label printing paper of this construction, the image-receiving layer portion 41 can be stuck on an article after forming an image on the receiving layer 43 and then releasing the image-receiving layer portion 41 from the support layer portion 42. For the easy-cut structure 32 by which the printing paper can be easily cut, the label printing paper has been subjected to the so-called half-cut treatment in which a cutting line 32a formed of a cut continuously formed over the entire width thereof is provided in only the image-receiving layer portion 41. There is also label printing paper in which a perforation 32b formed of cuts intermittently formed over the entire width over the entire thickness of the label printing paper composed of an image-receiving layer portion 41 and a supporting layer portion 42 is provided as the easy-cut structure 32 by which the printing paper can be easily cut, as illustrated in FIG. 17. In these side views, the cutting line 32a formed of a cut continuously formed over the entire width and the perforation 32b formed of cuts intermittently formed over the entire width are typically indicated by a solid line and a two-dot chain line, respectively.
By using the printing paper having such easy-cut structure 32 by which the printing paper can be easily cut, an image can be formed over the entire surface of a center portion 33 other than outside portions 34 outside the easy-cut structure 32 by which the printing paper can be easily cut as illustrated in FIG. 14. Therefore, the outside portions 34 of the printing paper on which an image has been formed are cut off from the easy-cut structure 32 by which the printing paper can be easily cut, whereby a print in which the image has been formed over the entire surface can be provided as illustrated in FIG. 12.
However, a print obtained by using the label printing paper subjected to the half-cut treatment as illustrated in FIG. 16 has to be carried in its original size including the outside portions 34. Such a large print is inconvenient for carrying. On the other hand, a print obtained by using printing paper provided with a perforation 32 as illustrated in FIG. 13 can be carried in a condition in which outside portions 34 have been cut off. However, its four corner edges are in a squarish form. Such a print having the four squarish corner edges involves a problem that it is hard to put into a holder such as a purse, pocket notebook or card case because the edge of the print strikes the holder or is caught thereby upon putting the print into the holder.
In the label printing paper subjected to the half-cut treatment, the image-receiving layer portion 41 can be easily separated from the supporting layer portion 42 and stuck on an article by striking a nail or the like against the position of the cutting line 32a along the upper surface of the supporting layer portion 42 of the outside portion 34 to insert the nail or the like between the image-receiving layer portion 41 and the supporting layer portion 42. In the printing paper provided with the perforation 32b on the other hand, when the outside portions 34 are cut off, the outside portions of the supporting layer portion 42 are also cut off. Accordingly, a print from which the outside portions 34 have been cut off involves a problem that it is difficult to insert a nail or the like between the image-receiving layer portion 41 and the supporting layer portion 42, and so the image-receiving layer portion 41 is hard to be separated from the supporting layer portion 42.